Quantum Information Processing最新文献

Quantum key distribution (QKD) is a secure communication method that relies on the inherent randomness of quantum mechanics to ensure information-theoretic security. The first and most widely used QKD protocol is BB84, and the proof of BB84’s security is vital. The discrete phase randomized BB84 protocol is a variant of the decoy BB84 protocol. It has been proven to be promising in the development of high-speed QKD systems. However, it still lacks an analysis with a finite number of pulses. This paper presents a comprehensive security analysis of the discrete phase BB84 protocol, using two different methods under different conditions. The analysis involves simulations and optimizations to determine the optimal parameter settings. It is confirmed that for a small number of finite pulses, i.e., (10^7), if the number of discrete phases exceeds 30, one can calculate the key rate by assuming that a continuous phase randomization process was in operation. On the other hand, for a relatively smaller number of discrete values, i.e., 16 discrete phases, we have developed a numerical method to calculate the key rate. We have confirmed that its performance is reduced but still acceptable with a finite number of pulses.

Let R be the finite chain ring (mathbb {F}_{p^{2m}}+{u}mathbb {F}_{p^{2m}}), where (mathbb {F}_{p^{2m}}) is the finite field with (p^{2m}) elements, p is a prime, m is a non-negative integer and ({u}^{2}=0.) In this paper, we firstly define a class of Gray maps, which changes the Hermitian self-orthogonal property of linear codes over (mathbb {F}_{2^{2m}}+{u}mathbb {F}_{2^{2m}}) into the Hermitian self-orthogonal property of linear codes over (mathbb {F}_{2^{2m}}). Applying the Hermitian construction, a new class of (2^{m})-ary quantum codes are obtained from Hermitian constacyclic self-orthogonal codes over (mathbb {F}_{2^{2m}}+{u}mathbb {F}_{2^{2m}}.) We secondly define another class of maps, which changes the Hermitian self-orthogonal property of linear codes over R into the trace self-orthogonal property of linear codes over (mathbb {F}_{p^{2m}}). Using the Symplectic construction, a new class of (p^{m})-ary quantum codes are obtained from Hermitian constacyclic self-orthogonal codes over R.

The way a new type of state called a hybrid state, which contains more than one degree of freedom, is used in many practical applications of quantum communication tasks with lesser amount of resources. Similarly, our aim is here to perform multi-quantum communication tasks in a protocol to approach quantum information in multi-purpose and multi-directional. We propose a hybrid multi-directional six-party scheme of implementing quantum teleportation and joint remote state preparation under the supervision of a controller via a multi-qubit entangled state as a quantum channel with (100%) success probability. Moreover, we analytically derive the average fidelities of this hybrid scheme under the amplitude-damping and the phase-damping noise.

We propose an effective scheme to predict nonreciprocal unconventional magnon blockade in a hybrid system composed of a rotating pump cavity, a signal cavity and a yttrium iron-garnet (YIG) sphere. The two cavities interact nonlinearly, and meanwhile, the signal cavity couples to magnon in the YIG sphere via magnetic dipole interaction. Based on the dispersive couplings between two cavities and between the signal cavity and magnon, the indirect nonlinear interaction is established between the pump cavity and magnon modes, which plays an important role in the generation of magnon blockade. The system exhibits nonreciprocal unconventional magnon blockade phenomenon when the pump cavity is driven from clockwise or counterclockwise directions. These phenomena occur in weak coupling and driving regimes, which could relax the requirements of the system parameters and may have potential applications in quantum information processing in hybrid systems.

In this paper, we first study the maximally commutative set in prime dimensional systems, which is a set of generalized Pauli matrices, and it can be used to detect the local discrimination of generalized Bell states. We give a simple characterization of prime dimensional maximally commutative sets, that is, a subset of a set of generalized Bell states, whose second subscript is a multiple of the first subscript. Furthermore, some sets of generalized Bell states which can be locally distinguishable by one-way local operation and classical communication (LOCC) are constructed by using the structural characteristics of prime dimensional maximally commutative sets. Based on these distinguishable generalized Bell states, we propose a (t, n)-threshold quantum secret sharing scheme. Compared with the existing quantum secret sharing scheme, it can be found that there are enough distinguishable states to encode classical information in our scheme, the dealer only needs to send entangled particles once to make the participants get their secret share, which makes the secret sharing process more efficient than the existing schemes. Finally, we prove that this protocol is secure under dishonest participant attack, interception-and-resend attack and entangle-and-measure attack.

This paper presents a study on the structure of 1-generator quasi-cyclic (QC) codes over the non-chain ring (R=mathbb {F}_{q}+umathbb {F}_{q}+vmathbb {F}_{q}+uvmathbb {F}_{q}), where (u^2=v^2=0,~ uv=vu), and (mathbb {F}_q) is a finite field of cardinality (q=p^r); p is a prime. A minimal spanning set and size of these codes are determined. A sufficient condition for 1-generator QC codes over R to be free is given. BCH-type bounds on the minimum distance of free QC codes over R are also presented. Some optimal linear codes over (mathbb {F}_q) are obtained as the Gray images of quasi-cyclic codes over R. Some characterizations of the Gray images of QC codes over R in (mathbb {F}_q) and (mathbb {F}_q+umathbb {F}_q~(u^2=0)) are done. As an application, we consider self-orthogonal subcodes of the Gray images of QC codes over R to obtain new and better quantum codes than those are available in the literature.

We present proper genuine multipartite entanglement (GME) measures for arbitrary multipartite and dimensional systems. By using the volume of concurrence regular polygonal pyramid, we first derive the GME measure of four-partite quantum systems. From our measure, it is verified that the GHZ state is more entangled than the W state. Then, we study the GME measure for multipartite quantum states in arbitrary dimensions. A well-defined GME measure is constructed based on the volume of the concurrence regular polygonal pyramid. Detailed example shows that our measure can characterize better the genuine multipartite entanglements.

As one of the most important branches of quantum information science, quantum communication is known for its unconditional security and efficiency. Nevertheless, the practical security of quantum key distribution protocols and quantum secure direct communication protocols is challenged due to the imperfections in experimental devices. Despite significant progress in theoretical and experimental research on the MDI-QSDC Protocol, challenges and unresolved issues remain. For example, further enhancing the scalability and system complexity of the protocol to meet the demands of large-scale quantum networks is necessary. In this paper, we propose a multi-party MDI-QSDC scheme based on multi-degree-of-freedom hyperentangled photons. Compared to the original MDI-QSDC protocol, our protocol allows multiple parties to participate in the information transmission process. For example, for four communicating parties, we can encode the information of three independent degrees of freedom so that each photon of each degree of freedom can transmit 2 bits of information. Moreover, all measurement tasks are performed by the fifth party, which can be untrusted or even completely controlled by eavesdroppers. The protocol is resistant to all possible attacks from imperfect measurement devices. It can eventually be extended to arbitrary degrees of freedom, allowing multiple parties to participate.

Quantum computing has the potential to solve many complex algorithms in the domains of optimization, arithmetics, structural search, financial risk analysis, machine learning, image processing, and others. Quantum circuits built to implement these algorithms usually require multi-controlled gates as fundamental building blocks, where the multi-controlled Toffoli stands out as the primary example. For implementation in quantum hardware, these gates should be decomposed into many elementary gates, which results in a large depth of the final quantum circuit. However, even moderately deep quantum circuits have low fidelity due to decoherence effects and, thus, may return an almost perfectly uniform distribution of the output results. This paper proposes a different approach for efficient cost multi-controlled gates implementation using the quantum Fourier transform. We show how the depth of the circuit can be significantly reduced using only a few ancilla qubits, making our approach viable for application to noisy intermediate-scale quantum computers. This quantum arithmetic-based approach can be efficiently used to implement many complex quantum gates.

In this article, we find several novel and efficient quantum error-correcting codes ((boldsymbol{mathcal{Q}})ecc) by studying the structure of constacyclic ((boldsymbol{{mathcal{C}}{mathcalligra{cc}}})), cyclic ((boldsymbol{{mathcal{C}}{mathcalligra{c}}})), and negacyclic codes (N(boldsymbol{{mathcal{C}}{mathcalligra{c}}})) over the ring ({A}_{k}={Z}_{p}left[{r}_{1},{r}_{2},dots ,{r}_{k}right])/(langle {{(r}_{b}}^{({m}_{b}+1)}-{r}_{b}), {r}_{l}{r}_{b}={r}_{b}{r}_{l}=0, bne lrangle ), where (p={q}^{m}) for m, ({m}_{b}in {mathbb{N}}), ({m}_{b} | left(-1+qright)) (forall b, l in left{1, text{to}, kright}), (qge 3) is a prime, ({Z}_{p}) is a finite field. We define distance-preserving gray map ({delta }_{k}). Moreover, we determine the quantum singleton defect ((mathcal{Q})SD) of (boldsymbol{mathcal{Q}})ecc, which indicates their overall quality. We compare our codes with existing codes in recent publications. The rings discussed by Kong et al. (EPJ Quantum Technol 10:1–16, 2023), Suprijanto et al. (Quantum codes constructed from cyclic codes over the ring(F_{text{q}}+{text{vF}}_{text{q}}+{v}^{2}F_{text{q}}+{v}^{3}F_{text{q}}+{v}^{4}F_{text{q}}), pp 1–14, 2021. arXiv: 2112.13488v2 [cs.IT]), and Dinh et al. (IEEE Access 8:194082–194091, 2020) are specific cases of our work. Furthermore, we construct several novel and optimum linear complementary dual (Lcd) codes over ({A}_{k}.)